Various apparatus are employed for determining the instantaneous position and/or rate of change of an article/body in motion. Such apparatus are commonly employed in manufacturing facilities where a work piece is conveyed along an assembly line and stopped/routed from one fabrication station to another. Generally, it is useful to record/store the precise location and/or velocity of the article/work piece in order to track useful parameters as such as efficiency, throughput, total capacity, rate of rejection/rework, etc. The instantaneous position of an article/work piece also may be used to initiate processes used in the fabrication of other assemblies/subassemblies.
One such apparatus, useful for describing the teachings of the present invention, is a mailpiece inserter system used for creating high-volume mail communications, e.g., mass mailings. Such mailpiece inserter systems are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mail communications where the contents of each mailpiece are directed to a particular addressee. Also, other organizations, such as direct mailers, use mail inserters for producing mass mailings where the contents of each mailpiece are substantially identical with respect to each addressee. Examples of inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. located in Stamford, Conn., USA.
In many respects, a typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (i.e., a web of paper stock, enclosures, and envelopes) enter the inserter system as inputs. Various modules or workstations in the inserter system work cooperatively to process the sheets until a finished mailpiece is produced. The precise configuration of each inserter system depends upon the needs of each customer or installation.
Typically, inserter systems prepare mailpieces by arranging preprinted sheets of material into a collation, i.e., the content material of the mailpiece, on a transport deck. The collation of preprinted sheets may continue to a chassis module where additional sheets or inserts may be selectively added in view of a targeted audience of mailpiece recipients. From the chassis module the fully developed collation may continue to yet other stations for further processing. That is, the envelopes may be closed, sealed, weighed, sorted and stacked. Additionally, the inserter may include a postage meter for applying postage indicia based upon the weight and/or size of the mailpiece.
In addition to the various fabrication stations described above, a mailpiece inserter typically employs a mailpiece tracking system along the feed path of the inserter. That is, to track and/or make adjustments to the mailpiece fabrication process, the tracking system records and monitors the instantaneous position/location of each mailpiece “in process.” As such, adjustments can be made to add different inserts and/or out-sort mailpieces which are discovered to have certain errors or deficiencies.
A typical mailpiece tracking system employs a plurality of photocells disposed at periodic and/or critical locations to ensure that each mailpiece is identified and tracked along the inserter feed path. Each photocell is disposed through aligned apertures formed in the inserter support deck so as to shine and/or receive reflected light in a direction orthogonal to the passing mailpiece. Moreover, the photocells are hardwired, in parallel, to a central controller/processor, e.g., 8051 boards. Light is shined on/reflected from a barcode identifier, or other distinguishing marks on the face of the mailpiece, and interpreted by the central processor. Each time a mailpiece passes a photocell, information concerning its identity and location are recorded/monitored.
While tracking systems which employ photocells have a long history of reliable service, the installation and the operational environment produces a variety of unique problems. More specifically, the large number of photocells required to obtain accurate and useable location data requires an extensive network of wiring beneath the inserter support deck. This extensive electronic network is laborious to install and similarly time-consuming to trouble-shoot should certain system errors be encountered. In large machines, wiring can span large distances, making it susceptible to electromagnetic interference (i.e., causing spurious signals). Furthermore, long wiring runs can impose resistance and impedance loads, which can degrade signal quality. Furthermore, the photocells are necessarily located in the mailpiece fed path where paper fibers and dust, from the thousands of envelopes processed hourly, are shed and collect on the support deck of the mailpiece inserter. In just several hours of operation, paper fibers can built to a significant thickness, cover the photocell apertures and occlude the transmission of light to/from the photocells. Consequently, the photocell apertures must be cleared of particulate matter on a regular/periodic basis. It will be appreciated, therefore, that mailpiece inserter systems which employ photocell position tracking systems are burdened by the cost of photocell installation, repair and maintenance.
A need, therefore, exists for a position/motion tracking system which is reliable, expedites installation, and facilitates maintenance/repair.